Personally being a Sr. Software Configuration Manager for many years (10+) I hear the terms mismatched in a variety of real life situations. It is not uncommon for non technical personnel due to the relative nature of the positions. They both have specific roles, needs and requirements that are similar but yet can be clearly divided in my opinion.
I believe the best way to describe the division of these roles is to focus on their relativity to interaction. Meaning this, Software Configuration Management focuses on the internal systems and environments, along with integration, deployment, release and management of source code. Where as Developer Operations (DevOps) focuses more on the operational aspect of externally faced application architecture, while maintaining a clear understanding of the code as it was intended for use and the practice of its environment. If the performance of a machine is showing signs of degradation, communication between multiple applications is faulty, business to business (BtB) communication and/or architecture limitations in relation to a production environment, then you would look to the Developer Operations for their diagnosis and solution.
Typically, in my experience, the Software Configuration Manager can do these things as well, but this takes away from their core focus of tracking, managing, and deployment of environment configurations and software revisions. Managing the software that allows the separation of duties, bug and defect tracking, project tracking, and the software development lifecycle and worflow. These tasks are not the core focus of Developer Operations and therefore less imperative, but still can be done.
I have seen many instances of the confusion of each, and in each there is some limited crossover. However, it is most important to think of the differences between the responsibilities of each of the independent positions in relation to their primary focus. Primarily when dealing with internally utilized systems and hardware to manage the configuration of environments and release of product, you would seek out a Software Configuration Manager. On the other hand, when dealing with system performance, monitoring, research and diagnosis of systems used by your customers, you should look to the Developer Operations or DevOps.
Now, this is not a meant as a rant, nor as a definitive answer, but rather a personal identification of the differences of each of the positions. I would like to know if I am well off base, or if things are made clearer by this answer.